1. Field of the Invention
This invention relates to a method of producing endo-.alpha.-N-acetylgalactosaminidase from microorganisms.
2. Description of the Prior Art
In recent years, it has been found the important functions of the sugar-chain portions of complex carbohydrates for cell differentiation, cell growth, cell recognition, and the onset of many diseases that involve malignant tumors, in living organisms.
For complex carbohydrates such as glycoproteins the sugar chains of the glycoproteins or the like are bound to the peptide chain of the glycoproteins either via N-glycosidic linkages or O-glycosidic linkages. Of these two kinds of sugar chains, the sugar chains with 0-glycosidic linkages mainly exist in blood group substances and in glycoproteins involved in immunity. It has been found that such sugar chains with 0-glycosidic linkages have a variety of important physiological functions. In order to further identify these functions, the structural investigation of the sugar chains is indispensable. For this kind of analysis of the structure of the sugar chains, the use of various glycosidases that have high substrate specificity for the sugar chain structure in complex carbohydrates provides an important means.
Of such glycosidases, endo-.alpha.-N-acetylgalactosaminidase) (endo-.alpha.-GalNAcase) can be used as an enzyme that acts on sugar chains with a Gal .beta.1.fwdarw. 3GalNAc structure in which the GalNAc is bound the serine or threonine residues of proteins, to cleave the O-glycosidic linkages; thus, the enzyme releases the sugar chains from the proteins. This action of the enzyme is shown in the following formula: ##STR1## wherein Gal is galactose, GalNAc is N-acetylgalactosamine, Ser is serine, Thr is threonine, and X and Y are peptide chains. In this way, because endo-.alpha.-GalNAcase can release sugar chains with O-gylcosidic linkages from proteins, this enzyme is important for the structural analysis of the sugar chains of glycoproteins.
Previously, the activity of endo-.alpha.-GalNAcase has been found in the culture medium of Clostridium perfringens or Diplococcus pneumoniae only. Also, the purification and the characterization of this enzyme are not yet satisfactory, which decreases its practical value.